I bought an AT&T Pantech C3B cell phone. How can I unlock it so that I can use my Sprint service with it?

Q:
I do have AT&T also, so I am able to use it, but I really wanted to use it for my sprint service. I guess I'll have to look for a small phone for that provider. Am I able to do the same with Sprint as I am with AT&T?

A: You can't.
Sprint uses CDMA technology. AT&T uses GSM technology. Two totally different things. Sorry.